It is well known that integrated circuits can suffer from a variety of failure mechanisms, some of which occur in the process or under use conditions.
Today's integrated circuits are both vertically and horizontally integrated and can incorporate multiple levels of metallization. The increased metallization has led to higher chip clock rates with increasing speeds becoming necessary. To permit defect-free production, failure mechanisms must be precisely located within the complex three-dimensional structure of the circuit.
Locating defects requires two types of instruments namely, sophisticated imaging systems and test equipment capable of exercising the circuit under normal clock operating rates. The image emission microscope localizes defects in integrated circuits. The emission microscope is based on the principle of recombinant radiation. In excess current drawing conditions, such that occurs during failure, electrons and holes in silicon recombine and relax, giving off a photon of light which is readily detectable by specialized sensors, for example, a CCD sensor. Semiconductor manufacturers typically perform this technique on wafers and on delidded or decapsulated finished devices. The technique is utilized to locate the exact location of defects both on the chip face and beneath overlying metallization, thereby permitting location of defects within the 3-dimensional environment of the circuit.
Prior art for biasing of the chip during such testing has generally included two-channel DC power supplies or curve tracers which provide basic power requirements to the chip. Consequently, in the design of semiconductor devices, it is often desired to analyze the current flow through the various circuits. Such analysis is particularly beneficial with respect to integrated circuit to isolate it points of potential failure.
Avalanche breakdown can be analyzed by observing emitted light. The light is emitted as a result of electroluminesence of silicon avalanche. Thus, light emission in this situation enables the detection and location of areas of current flow.
Oxide defects can be detected by observing the light emitted upon application of a current. By observing the emitted light, the points of failure of damaged products can be determined and the analysis of design flaws and/or process flaws can be advantageously undertaken.
Finally, the profile and detailed effects of an ESD (electrostatic discharge) event in an integrated circuit may be determined. During ESD, P-N junctions become forward biased or even go into avalanche breakdown. In either case, light is emitted. By profiling the emitted light pattern, the profile of ESD event can be observed and the area of dissipation of the ESD energy can be determined.
FIG. 1 illustrates a prior art intensified camera 50 and a CCD camera 60.